Radar antenna consisting of a linear source with its directivity in a plane at rightangles to the line, obtained by a dielectric structure



2: 3 m a n OLHKUH KUUM Feb. 8, 1966 G. BORGIOTTI 3,234,558

RADAR ANTENNA CONSISTING OF A LINEAR SOURCE WITH ITS DIRECTIVITY IN A PLANE AT RIGHT ANGLES TO THE LINE, OBTAINED BY A DIELECTRIC STRUCTURE Filed March 8, 1963 I I 2 I 9 I gi Ll. Q t z & V i {I} 1;}

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at: H M H M F 7v n INVENTOR Giorgio Borgiofli m h: J BY I m x {N W M* ATTORNEYS United States Patent 3,234,558 RADAR ANTENNA CONSISTING OF A LINEAR SOURCE WITH ITS DIRECTIVITY IN A PLANE AT RIGHT ANGLES TO THE LINE, OBTAINED BY A DIELECTRIC STRUCTURE Giorgio Borgiotti, Rome, Italy, assignor to Seienia-Industrie Elettroniche Associate S.p.A., Rome, Italy Filed Mar. 8, 1963, Ser. No. 263,956 Claims priority, application Italy, Sept. 26, 1962, 18,721/ 62 1 Claim. (Cl. 343-756) The present antenna refers to a slot array antenna whose directivity in the plane at right angle to the guide is fulfilled by using a cylindrical dielectric structure. It is often necessary in shipboard radar apparatus to have a fan beam antenna, namely an antenna having a beam very narrow in the horizontal plane and rather broad in the vertical plane. An antenna often used for this kind of radar is the slot array antenna, in which the formation of the vertical beam is obtained by using a sectorial horn.

The present invention refers to a different way of obtaining the vertical beam of the antenna through the use of a special dielectric structure.

According to the invention an array of slots in a wall of a guide radiates through a shaped dielectric structure.

This invention will be described with reference to the drawings showing one preferred embodiment of the invention.

In the drawings:

FIGURE 1 is a perspective view of the antenna according to this invention, particularly cross sectioned so as to show the internal structure.

FIGURE 2 is a front view, partially cross sectioned according to the section lines II-II and IlI-III of FIG- URE 3.

FIGURE 3 is a cross-sectional view.

With reference to the drawings, the antenna comprises a guide 3, with slots through the narrow side, forming an array of elementary radiators. Each slot irradiates into a space which is defined by two metal plates 4.

Between the adjacent slots, the metal blocks 2 reduce (towards the direction parallel to the guide) the dimension of the space into which the single slots irradiate, down to a value lower than one half of the length of the working wave. Said spaces defined by the blocks 2 and the plates 4 form therefore guide portions to cutoff for the undesired polarization components.

Downstream of the metal blocks, the matching of the wave impedance between the field of the aforesaid spaces and that sustained by the dielectric radiating structure, is embodied by a portion which is defined by the metal walls 4 having two dielectric layers adherent to the walls themselves. The radiating dielectric structure 1, is embodied by means of two thin layers of fiberglass terminated by a circular half cylindrical closure. The antenna in the particular embodiment as hereinbefore described is centrally fed and said feeding is obtained by a probe 5 entering into the guide 3, through a hole provided in the wide side of the intermediate section of the guide.

The two ends of the guide 3 are terminated by two metal plates or by two microwave absorbing elements depending upon the type of the used linear array (stationary waves or travelling waves).

The present invention has been described in one preferred embodiment, but various modifications may be made without departing from the scope of the present invention.

What -I claim is:

A microwave slot antenna comprising in combination a waveguide comprising a first U-shaped metal box having a narrow wall and two broad walls, a second U-shaped metal box having a narrow wall and two broad walls, said second box being rigidly secured within said first box to cause the narrow wall of the first box to close the open side of the second box, said narrow wall of the second box having a series of equispaced slots, a series of U-shaped metal blocks arranged within and filling the cross-section area of the interspace formed by said first and second box and between said slots to separate each slot from the other, a U-shaped elongated dielectric structure having two broad walls and a semicircular narrow wall and inserted with its open side into said first ox to contact with said metal blocks, a substantial portion of said dielectric structure projecting outwardly from said Waveguide, and a central feeding probe entering into said second box through one broad wall of said first and second box and through the central one of said metal blocks.

References Cited by the Examiner UNITED STATES PATENTS 2,730,717 1/1956 Katchky et al 343--771 X 2,817,084 12/1957 Clapp et al. 343-770 3,002,190 9/1961 Oleesky 343-872 3,004,259 10/1961 Shanks 343--771 3,007,166 10/ 1961 Hame 343-771 3,031,664 4/ 1962 Wielobob 34377l 3,146,449 8/1964 Serge et a1 343756 X FOREIGN PATENTS 602,689 6/1948 Great Britain.

HERMAN KARL SAALBACH, Primary Examiner. W. K. TAYLOR, P. L. GENSLER, Assistant Examiners. 

